1. Technical Field
The present disclosure relates to open or endoscopic instruments and method for treating tissue, and more particularly, the present disclosure relates to surgical instruments including an assembly for determining tissue type and the condition of the tissue being treated utilizing electrical property measurements of the tissue.
2. Background of Related Art
A hemostat or forceps is a simple plier-like tool that uses mechanical action between its jaws to constrict vessels and is commonly used in open surgical procedures to grasp, dissect and/or clamp tissue. Electrosurgical forceps utilize both mechanical clamping action and electrical energy to affect hemostasis by heating the tissue and blood vessels to coagulate, cauterize and/or seal tissue.
Over the last several decades, more and more surgeons are complementing traditional open methods of gaining access to vital organs and body cavities with endoscopes and endoscopic instruments that access organs through small puncture-like incisions. Endoscopic instruments are inserted into the patient through a cannula, or port, that has been made with a trocar. Typical sizes for cannulas range from three millimeters to twelve millimeters. Smaller cannulas are usually preferred, which, as can be appreciated, ultimately presents a design challenge to instrument manufacturers who must find ways to make surgical instruments that fit through the cannulas.
As mentioned above, by utilizing an electrosurgical instrument, a surgeon can either cauterize, coagulate/desiccate and/or simply reduce or slow bleeding, by controlling the intensity, frequency and duration of the electrosurgical energy applied through the jaw members to the tissue. The electrode of each jaw member is charged to a different electric potential such that when the jaw members grasp tissue, electrical energy can be selectively transferred through the tissue.
Bipolar electrosurgical instruments are known in the art, as are other electrosurgical instruments. Commonly owned U.S. Patent Application Publication No. 2007-0062017, discloses a bipolar electrosurgical instrument, the entire contents of which is hereby incorporated by reference herein. Conventional bipolar electrosurgical instruments may include a cutting blade, fluid applicator, stapling mechanism or other like feature, in various combinations.
Different types of tissues, i.e. vessels, ligaments, may require different energy delivery configurations to effect proper sealing. While a specific energy delivery configuration may be adequate for treating an artery or vein, the same energy delivery configuration may not be suitable for treating a ligament. Although a majority of the time the type of tissue being treated is either known or visually apparent, there may be instances where a surgeon is unable to visually determine the type of tissue being sealed. Treating non-target type tissue with an energy configuration configured for a target type tissue may cause damage to the non-target tissue and/or result in failure to effect proper treatment.
Traditional methods for identifying tissue within the body are based on sensing physical characteristics or physiological attributes of body tissue, and then distinguishing normal from abnormal states from changes in the characteristic or attribute. For example X-ray techniques measure tissue physical density, ultrasound measures acoustic density, and thermal sensing techniques measures differences in tissue heat. A measurable electrical property of tissue is its impedance; i.e., the resistance tissue offers to the flow of electrical current through it. Values of electrical impedance of various body tissue are well known through studies on intact human tissue or from excised tissue made available following therapeutic surgical procedures.
Various methods and apparatus for measuring tissue electrical properties are known. For example, U.S. Pat. No. 5,380,429 to Withers, discloses a method and apparatus for displaying multi-frequency bio-impedance, and U.S. Patent Publication No. 2006/0004300, discloses a method of multi-frequency bio-impedance determination, the entire contents of each of which are hereby incorporated by reference herein.
Once the type of tissue is identified, determining the condition or state of the tissue is important in effectively and properly treating the tissue. Diseased, ischemic, or otherwise compromised tissue may not adequately seal, or may require alteration to the energy delivered to the tissue. It is well documented that a decrease in electrical impedance occurs in tissue as it undergoes cancerous changes. Using any of the known methods for measuring tissue impedance, the tissue impedance may be measured, and the resulting measurements may be compared against known impedance measurements for like tissue. Difference between the readings may be used to indicate the condition of the tissue. Thus, knowledge of the electrical properties of tissue may be used to identify the type of tissue and/or the condition of that tissue.